I have all of these pitchers starting today. Im not really concerned with Wins because I am in 2nd in Wins by a pretty nice lead. I am very concerned with my ERA and WHIP though. A Win would be nice but im more worried about my ERA and WHIP. Who should I start? Who should I bench? Thank you for your time guys!

Halladay and Willis would be my first choices. Both are pitching well and are on hot streaks. Their oppositions are the weaker of the 4, although I'll note that Brewers are at home in their launching pad.

Buehrle and Pineiro - Buehrle has had 2 or 3 quality starts, but I still wouldn't risk him yet. Pineiro is a wild card, I like him, but I also would be nervous each time he pitched when I had him on my team. He has the win potential, but more because the Mariners score a ton of runs.

That being said, I would probably rank them Halladay, Willis, Pineiro, Buehrle.

Halladay is a must start. He is on something like a 8 game winning streak, and the Pirates are a pretty weak offensive team with a terrible pitching staff and bullpen. The Jays have a ridiculously potent offense, so he pretty much should win no matter how bad he pitches. The only concern that I'd have is that SkyDome is starting to act like an extreme hitters park this year, while it's been pretty neutral in the past.

I would also start Pineiro. It's at home, in a pitcher's park; Pineiro is a quality pitcher and Montreal is playing without Vlad, so they don't exactly rank as a scary offense. Willis should be a decent start, but I wouldn't fully trust him. Rookie pitcher are a constant risk of getting lit up, although the Brewers are a pretty weak team, so I'd probably chance it. I would personally get rid of Willis in a non-keeper as soon as he has two straight bad starts, because he is pitching way over his head right now and I seriously doubt he's the second coming of Kerry Wood.

I would leave Buerhle on the bench for this one. Although he has been coming around, US Cell is a hitter's park, and Bonds and co. have the ability to rake him over the coals if he's even a bit off. If he does well in this start against the strong Giants offense, it's probably a sign that it's safe to use him most of the time again.